From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f170.google.com ([209.85.223.170]:52020 "EHLO mail-ie0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750817AbaGCL0p (ORCPT ); Thu, 3 Jul 2014 07:26:45 -0400 Received: by mail-ie0-f170.google.com with SMTP id tr6so43511ieb.29 for ; Thu, 03 Jul 2014 04:26:45 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <53B51560.2040603@cn.fujitsu.com> References: <1404207001-7510-1-git-send-email-quwenruo@cn.fujitsu.com> <53B445F5.6060709@libero.it> <53B4A3C7.1020805@cn.fujitsu.com> <53B51560.2040603@cn.fujitsu.com> From: Tobias Geerinckx-Rice Date: Thu, 3 Jul 2014 13:26:24 +0200 Message-ID: Subject: Re: [RFC PATCH] Revert "btrfs: allow mounting btrfs subvolumes with different ro/rw options" To: Qu Wenruo Cc: kreijack@inwind.it, linux-btrfs@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 3 July 2014 10:33, Qu Wenruo wrote: > Oh, sorry for my confusing words. And I probably should have waited for my frustration with my mail client/device/public transport to subside before panicking^Creplying. I use a combination of ro & rw (not insanely nested) subvolumes on a few pseudo-embedded home/office servers and would like to keep that arrangement working if possible. I'm also aware that it doesn't protect against all possible bugs. > To make it clear, when mentioning 'the whole disk(or partition whatever)' I mean the FS_TREE. > (Of course not the default subvolume) > > The problem is that, even you mount a subvolume ro, you can still change contents in the subvolume > through its rw parent subvolume. > And if a subvolume can still be modified, the ro mount lose it meaning. That makes so much more sense than my original reading, which was weird and wrong and implied strange subvol-5-only magic. Sorry! > So we need special rules to prevent such things. Not that it matters, but: agreed. Tobias